Solid ink (also known as phase-change ink) image-producing devices conventionally employ ink supplied in solid form through a drop tube, either as pellets or as colored-ink sticks. In general, phase change inks are in solid form at ambient temperature, but the ink must be converted to liquid form and transported to the print head, where the ink can be ejected as drops or jets. Generally, this phase change is accomplished by melting the solid ink in a solid-ink melter tank. A melter assembly for large ink sticks includes a heating element with openings, which allow liquefied solid ink to pass through is disclosed in U.S. application Ser. No. 12/362,579 filed Jan. 30, 2009. Another U.S. application Ser. No. 12/638,863, filed Dec. 15, 2009, discloses a solid-ink melter apparatus including a heating element designed as an array of spaced apart fins, with a number of heat transfer elements passing through the fins. Liquefied solid ink is subsequently supplied to a print head of the image-producing device, forming jets of ink that print on the target media. When the ink droplets contact the printing media, they quickly solidify to create an image in the desired pattern.
Typically, heating elements in the solid-ink melter tank heat the air present in the solid-ink melter tank. In the absence of a forced airflow path, the hot air rises from the solid-ink melter tank into the drop tube, which heats the metering valve and the solid ink in the solid-ink supply tank. As the drop tube's temperature rises, some of the incoming solid ink partially melts and clings to the drop tube and the associated components, such as metering valves, leading to clogging of the drop tube and the associated components.
An electric cooling fan supplying cool air to the drop tube and the associated components may offer a solution to the problem. Sudden power failure, however, can cause the electric cooling fan to stop, leading to clogging of the metering valve, the solid-ink supply tank, the drop tube, and the associated components.
Therefore, a need exists for a mechanism to maintain the solid-ink drop tube and the associated components at a lower temperature.